Process of preparing cellulose for nitration



Patented Sept. 5, 1933 Ubll i" n STATES Parser @i'FlCE PROCESS OF PREPARKNG CELLULOSE FOE NITRA'IION No Drawing.

8 Claims.

This invention relates to an improvement in the process of paring nitr cellulose whereby suitable cellulosic materials are put in such a state of subdivision to render them capable of being and un o ,ily nitrated by any of the cds, and particularly in the process described in a co-pending application Serial No. 113,995, filed July 1, 1928. More particularly my invention relates to a process whereby relatively cheap forms of cellulosic raw materials, heretofore not suitable for nitration, be cheaply rapidly brought to a condition in which the cellulose may be uniformly pidly nitrated to produce a very high grade of nitrocellulose.

My process may be used for producing such a ate of subdivision as to render particularly suitable for nitration any form of suitable cellulosic raw materials, but is particularly concerned with the cheaper forms such as are commonly known 3 wood pulp, pulp lap, dry pulp, lap board and the like.

in order to obtain a satisfactory grade of nitrocellulose from wood pulp cellulose, it has heretofore been necessary to use special, and relatively expensive forms s ch as tissue paper. It has been cessary to use these special forms of wood cellulose because when attempts are made to nitrate the ordinary forms of wood pulp cellulose, such as pulp board, pulp lap, dry pulp and the like, the nitrating acid does not penetrate thru the dense compact fibers. The result is that only the surface is properly nitrated,-while the interior portions remain substantially unchanged. On the other hand, when tissue paper, which is only a f ew fibers in thickness is used, the nitrating acid will penetrate to the center of the sheet, and a fairly uniform nitrocellulose is obtained. Such special forms of cellulose, however, are relatively expensive, and a tissue paper suitable for nitration is usually more expensive than cotton linters, which has resulted in the very extensive use of cotton linters as a raw material for nitrocellulose.

My process eliminates the necessity of using such special forms of cellulosic raw materials as Application April 16, 192'? Serial No. 184,435

I obtain such a condition by pulling'or tearing apart the compact forms, so that the resulting product is in a fluffy, loose condition instead of in the original dense felted condition. When in this light fiuify condition the cellulose fibers which have been pull d or torn apart are readily surrounded by the nitrating acids during nitration, and a rapid and uniform nitration takes place resulting in a nitrocellulose having superior qualities as to'uniforinity, rate of solubility and clarity of solutions produced therefrom.

Furthermore, my process permits the use of cheap forms of certain preferred types of modified cellulose, as for example certain grades of bleached wood pulp relatively high in oxycellulose and hydrocellulose, as raw materials for the production of unmodified low viscosity nitrocellulose as described in a co-pending application Serial No. 119,995, filed July 1, 1926.

Another advantage is .1116 rapid rate at which nitration takes place with cellulose prepared by my process. This I believe to be due to the fact that practically every fiber comes in contact with the nitratin'g acid as soon as the fluffy, disintegrated cellulose is placed in the acid.

I have found by experiment that the methods of disintegrating the cellulosic material must be adapted to the particular form of aggregation in which the raw material is received for processing. I have found for example that methods suitable for disintegrating cotton rags must be modified for disintegrating lap board. Even with lap board itself it will readily be seen that the exact mechanical arrangement must be modified somewhat if the lap board to be disintegrated is in the form or" a roll rather than in slabs or sheets. While many types of machines are suitable for my purpose, I will describe the mechanical action of one preferred type Where the cellulose fibers are torn or pulled or abraded from the compact stock such as dry pulp, lap board and the like, into loose, fluffy, comminuted cellulose which is for the most part in the form of substantially individual fibers free and separate from each other instead of in the original felted or matted form. Cellulose in this loose fiuify condition is especially suitable forrapid and uniform nitration.

In the case of lap board in sheets or slabs the edge of a bundle of these boards is pressed normal to the tangent at the point of contact against a rotating circular wire brush of a width greater than the width of the bundle whose edge is undergoing abrasion against it. This rotating wire brush should preferably be made of a plurality of stiff metal wires firmly secured radially in a strong hub, and the whole rotated at such a speed as will cause the material to be abraded into substantially individual fibers. The wire bristles should preferably radiate out from the hub a uniform distance so that they present to the edge of the material undergoing disintegration a continual and uniform action of combing out from the compact lap board the individual cellulose fibers and carry along these fibers for some distance by the rotation and finally throw them free of the wire wheel by centrifugal force. t is convenient to surround this wire wheel with a collecting chamber connected to an exhaust fan in order to draw the fibers from the disintegrating zone, and move them into a cyclone tower or cloth bags by means of the air current produced by the fan. Classification may be used as part of my process to remove any pieces of fiber that have been incompletely disintegrated. Such classification may be accomplished by any suitable method such as air flotation or screening which are well known.

Where the lap board is in the form of a roll, the material may be unreeled mechanically and fed to the rotating wire wheel by a conveyor which constrains the edge of one or several thicknesses against the periphery of the rotating wire wheel.

For other types of suitable cellulose raw material such as cotton rags, pulp board trimmings and the like, it is preferable to first tear down the material to small pieces by means of some suitable apparatus such as a pronged carder which is a well known disintegrating machine used in the manufacture of rag paper. The sotorn cellulosic fragments may then be fed into a disintegrator composed of a plurality of wire brushes so arranged that the fragments are forced to pass between the ends of the wire bristles of said brushes rotating in opposite directions at different speeds with their axes parallel, and their bristle ends contiguous. The fragments are constrained to pass between the wire bristle ends by the rotation, and are disintegrated to substantially single fibers by the abrasion of the bristle ends moving in opposite directions.

1 Similar states of disintegration can be secured by other mechanical devices having a carding or combing action, such as a modified form of a picking machine.

It is obvious that many variations are possible as to the type of machinery used and the method of handling the oellulosio material both during and after the disintegration. It is to be understood that I do not limit myself as to the mechanical means of carrying out this step of proper disintegration of suitable cellulosic raw materials to a loose, iluffy, fibrous form suitable for the manufacture of nitrocellulose, and that the disintegration may be accomplished by any suitable type of machine without departing from the spirit of my invention.

Where I herein use the term comminuted in connection with the disintegrated condition of the cellulose, it is intended to mean that the material is in the most part in the form of substantially individual fibres free and separate from each other instead of being in the original felted or matted form.

The present application is a continuation in part of my earlier application Serial No. 119,995, filed July 1, 1926.

What I claim is:

1. In the manufacture of nitrocellulose from felted cellulose fibers, the steps of subjecting the dry felted material to a mechanical disintegrator capable of separating the individual fibers, assembling the separated fibers into a fiuify amorphous incoherent mass, and nitrating the fluffy mass.

2. In the manufacture of nitrocellulose from lamp board made from cellulose fibers, the steps of subjecting the dry lap board to a mechanical disintegrator capable of pulling the fibers from the lap board, assembling the fibers into a fluffy amorphous incoherent mass, and nitrating the fiufiy mass.

3.'In the manufacture of nitrocellulose from chemical wood pulp, the steps of forming a dried felted mass of wood pulp, subjecting the dried felted mass to the action of a mechanical disintegrator to pull fibers from the mass, assembling the fibers into a luffy amorphous incoherent mass, and nitrating the fluffy mass.

e. In the manufacture of nitrocellulose from cellulose fibers characterized by lengths corresponding to the lengths of fibers of chemical wood pulp, collecting the fibers substantially individually, assembling the fibers into a fluffy amorphous incoherent mass, and nitrating the fiuify mass.

5. In the manufacture of nitrocellulose from felted cellulose fibers, the steps of subjecting the dry felted material to a mechanical disintegrator capable of separating the individual fibers, classifying the product to remove particles not completely disintegrated into separate fibers, assenn bling the separated fibers into a flufiy amorphous incoherent mass, and nitrating the fluffy mass. 115

6. In the manufacture of nitrocellulose from lap board made from cellulose fibers, the steps of subjecting the dry lap board to a mechanical disintegrator capable of pulling the fibers from the lap board, classifying the product to remove particles not completely disintegated into separate fibers, assembling the fibers into a fluffy amorphone incoherent mass, and nitrating the fiuffy mass.

7. 'In the manufacture of nitrocellulose from chemical wood pulp, the steps of forming a dried felted mass of wood pulp, subjecting the dried felted mass to the action of a mechanical disintegrator to pull fibers from the mass, classifying the product to remove particles not completely disintegrated into separate fibers, assembling the fibers into a fiuify amorphous incoherent mass, and nitrating the fiuffy mass.

8. In the manufacture of nitrocellulose from cellulose fibers characterized by l ngths corresponding to the lengths of fibers of chemical wood pulp, classifying the product to remove particles not completely disintegrated into separate fibers, collecting the fibers substantially individually, assembling the fibers into a fluffy amorphous incoherent mass, and nitrating the fiuily mass.

WILLIAM COURTNEY WILSON. 1 r as 

